Recently, with the explosive prevalence of the Internet, a LAN (Local Area Network) is frequently constructed in offices, houses and the like.
Because cable wiring is troublesome, there is an increasing need for so called wireless LANs which construct a LAN wirelessly, which is aided by progress in digital wireless communication technologies. Further, wireless communication devices which constitute such a wireless LAN are expected to be used in large numbers, because the devices can be used in mobile terminals, such as notebook computers in mobile environments.
As a representative technology of the wireless LAN, there is IEEE 802.11 which has already been standardized by IEEE (Institute of Electrical and Electronics Engineers). This standardized technology defines from a physical layer to a MAC (Media Access Control) layer, being a lower layer of a data link in an OSI model, and can be replaced with Ethernet™ which is a wired LAN transmission channel. Further, IEEE 802.11 can provide a roaming function as an additional function due to being wireless.
Recently, in order to transmit/receive video image data or audio data wirelessly, a wireless AV system using such a wireless LAN is proposed.
Generally, a wireless AV system has a problem that video image data to be transmitted/received deteriorates due to transmission errors.
Patent Document 1 (PCT international publication No. WO 01/006795 (publication date; Jan. 25, 2001)) discloses an image decoding method in which a transmission error is detected by an image header included in video image data, and when a transmission error is detected, video image data is temporarily stored, repetition of a header different from the image header is detected, and based on this repeated header, temporarily stored video image data is decoded, and thereby deterioration of the video image data is prevented.
In a conventional wireless AV system, when one controlling device (such as an AV amplifier) controls a plurality of controlled devices (such as a video deck, a DVD player, a stereo, and a TV), the controlling device transmits control data by wireless to each of the controlled devices. Namely, the controlling device causes a data transmitting/receiving unit thereof to sort and transmit control data to each of the controlled devices.
As a result, the more controlled devices one controlling device has to control, the larger throughput is necessary for sorting of control data items in a data transmitting/receiving unit included in the controlling device, that is, the larger throughput is necessary for discriminating control data items, which makes it difficult for the controlling device to promptly control the controlled devices, with a result that the whole of the wireless AV system does not operate smoothly.
The present invention is made in view of the foregoing problems, and its object is to realize a wireless control system in which, even when the number of controlled devices which the controlling device has to control increases, a throughput for discriminating control data in the controlling side does not increase, and the whole of the wireless AV system can be smoothly operated.